First discovered in 1950, metam sodium, also sold under the trade names
Vapam, Busan, and Sectagon II, degrades rapidly to methylisothiocyanate,
the product's primary bioactive agent (Budavari 1994). Used as part of an
Integrated Pest Management system, metam sodium is a broad spectrum soil
fumigant that can be used to control nematodes, weeds, and fungi affecting
a variety of economically important fruit and vegetable crops. Overall,
metam sodium is considered a cost effective, technically viable
alternative to methyl bromide for controlling soil pests affecting high
value fruit and vegetable crops in Florida and California.
Metam sodium is a readily available, moderately toxic, versatile
pesticide product. For over three decades, metam sodium has been used in a
variety of experimental and commercial applications. By using metam sodium
to treat soils prior to planting, fruit and vegetable growers can control
tough annual weeds, reduce nematode populations, and control soil-borne
pathogens. In California, because of the low cost, ease of application,
safety, and effectiveness in controlling soil pests, over 8 million pounds
of metam sodium were used in the production of melons, peppers, tomatoes,
potatoes, strawberries, nurseries, ornamentals, cut flowers, container
plants, forest tree seedlings, citrus, grapes, almonds, artichokes,
asparagus, and carrots (CDPR 1995). In general, metam sodium reduces
competition from soil pests, promotes healthier crops and higher yields,
provides early uniform crop maturity and fruit ripening, and allows
growers to greatly increase economic returns by achieving maximum early
season yields (ICI 1992).
* Cost-effective method to control tough annual weeds, reduce nematode
populations, and control soil-borne pathogens prior to planting fruits and
vegetables.
* Versatile product used for over three decades. Has been shown to reduce
competition, improve plant growth, and increase yields.
Many researchers have cited metam sodium as a potential alternative to
methyl bromide fumigation, and metam sodium's low cost and wide-range of
control makes it a strong candidate for fumigation on many crops (Braun
and Supkoff 1994, Noling and Becker 1994, Yarkin 1994). Metam sodium is
registered for use in controlling a wide array of soil-borne pests. It can
be used to control weeds (e.g., bluegrass, bermudagrass, chickweed,
dandelion, ragweed, henbit, nutsedge, and wild morning glory), nematodes,
and soil diseases caused by species of Rhizoctonia, Fusarium, Pythium,
Phytophthora, Verticillium, Sclerotinia. Metam sodium is also useful in
Integrated Pest Management systems, as metam sodium can be used in
conjunction with resistant varieties, improved sanitation techniques,
biological control agents, and soil pasteurization (i.e., solarization,
hot water, or steam) (Noling and Becker 1994). Overall, metam sodium use
could be expanded across a wide range of fruit and vegetable crops
including tomatoes, strawberries, and peppers which currently account for
nearly 60 percent of domestic methyl bromide consumption (EPA 1994).
Improved growth responses and yield increases have been experimentally
and commercially documented (Larson and Shaw 1994, Olson and Noling 1994,
Cook and Keinath 1994, ICI 1992). In the production of carrots and
tomatoes, metam sodium has been used to significantly reduce populations
of stubby root (Paratrichodorous sp.) and root-knot nematode (Meloidogyne
sp.) prior to planting (ICI 1992).
A fresh market tomato study comparing metam sodium and methyl bromide
fumigation to an untreated control reported that yields and fruit quality
obtained with metam sodium were equivalent to those achieved with methyl
bromide fumigation (Cook and Keinath 1994). Also, results of a study
performed by Dr. Noling and Dr. Olson of the University of Florida
investigating the use of metam sodium on tomatoes indicated that yields
achieved with metam sodium were 85 percent of the methyl bromide yields
(Olson and Noling 1994). Additionally, in two strawberry field trials,
metam sodium was applied at 75 gallons per acre through sprinkler system;
methyl bromide/chloropicrin was applied at 325 lbs per acre. Overall,
during the early part of the season, yields achieved with metam sodium
were 26 percent greater than those obtained with methyl bromide. Although
methyl bromide yields for the overall season were 14 percent greater than
yields achieved with metam sodium, because metam sodium treatment costs
were one third less than methyl bromide costs and higher early season
yields achieved by metam sodium received significantly higher prices,
economic returns with metam sodium were greater than those achieved by
using methyl bromide (ICI 1992).
Although growers have historically been frustrated with metam sodium's
soil distribution characteristics and variations in pest control, research
and advances in application techniques have the potential to increase the
consistency and efficacy of metam sodium as a soil fumigant. Effectively
using metam sodium to control pests currently treated with methyl bromide
will require some low-cost modifications of cropping systems, including
the adoption of drip irrigation systems, narrower bed widths, multiple
drip tubes per bed, and planting practices which place plants closer to
drip tubes (Noling and Becker 1994).
To effectively use metam sodium, the applicator must follow the
recommendations provided by the product label, including considerations of
the soil conditions, methods of application, application rates, and the
factors influencing the release rate. In most cases, 25 to 100 gallons of
metam sodium are applied per treated acre as a liquid and then
incorporated into the soil through tilling and irrigation (Braun and
Supkoff 1994). An important consideration for ensuring effective
application is placement of the material in the soil profile. Metam sodium
is most effectively applied through drip tape if it is applied no more
than 6 inches off center and 2 to 3 inches deep. Metam sodium can also be
applied through sprinkler or flood irrigation. The release rate of metam
sodium depends on several factors including soil temperature, texture,
moisture and pH. Prior to application the seedbed must be prepared by
ensuring that it is free of clods and by receiving a preplant fertilizer
treatment. Additionally, soil moisture must be at least 50 to 75 percent
of field capacity, and soil temperatures must be between 40 F and 90 F in
the top 2 to 3 inches (ICI 1992).
Metam sodium is not a restricted use pesticide, and does not have to be
applied by a certified applicator. In addition, because metam sodium is
water soluble and has low volatility, it is the only soil fumigant that
can be applied through irrigation systems (ICI 1992). In addition,
although metam sodium has a high aquatic toxicity rating, in general, the
environmental and health risks posed by metam sodium are lower than those
posed by methyl bromide. One of the greatest advantages to the use of
metam sodium, however, is the low cost. Although supplemental pest control
activities may be required and would increase the total application costs,
metam sodium is safer and easier to use than methyl bromide and it costs
less. The attached table compares the costs of metam sodium and methyl
bromide for soil fumigation treatments. The average cost of metam sodium
ranges from $5.40 to $7.40 per gallon (Asgrow 1994), with typical
application rates ranging from 75 to 100 gallons per acre (Braun and
Supkoff 1994). Total application costs can average between $750 to $1,000
per acre. By comparison, methyl bromide application costs are estimated to
range from $1,200 to $1,500 per acre. Overall, because of its familiarity,
availability, effectiveness, and low cost, metam sodium is possibly one of
the highest profit alternatives to methyl bromide for the production of
fruits and vegetables in the United States (Yarkin 1994).
Fumigant:Metam sodium
Cost Per Unit ($): $5.40 - $7.40 per gallon
Units Per Acre: 75 - 100 gallons
Additional Costs: Labor/Tarp
Estimated Cost Per Acre: $750 - $1,000
Fumigant: Methyl Bromide
Cost Per Unit ($):$1.12 - $1.64 per pound
Units Per Acre: 180 - 400 pounds
Additional Costs:Contract Fumigation
Estimated Cost Per Acre:$1,200 - $1,500
Source: Asgrow 1995, Lykes Agrisales 1995, Tjosvald 1995.
Asgrow 1995. Price Quote. Active Ingredient Prices for Vapam® and
Methyl Bromide. Asgrow Chemical, Immokalee, FL.
Braun and Supkoff 1994. "Options to Methyl Bromide for the Control
of Soil-Borne Diseases and Pests in California with Reference to the
Netherlands". Adolf Braun and David Supkoff, Pest Management Analysis
and Planning Program, California Environmental Protection Agency,
Department of Pesticide Regulation, Sacremento, CA. July 1994.
Budavari (ed.) 1989. The Merck Index. Merck & Co. Rahway, NJ
Cook and Keinath 1994. Metam sodium as an alternative soil fumigant to
methyl bromide in fresh market tomatoes, 1993. F&N Tests 49:160.
CDPR 1995. California Department of Pesticide Regulation, Sacremento,
California California Pesticide Use Report, University of California,
Davis, CALLIPM, Pesticide Use Summary Database, April 1995.
EPA 1994. Methyl Bromide Consumption Estimates. U.S. Environmental
Protection Agency, Stratospheric Protection Division, Washington, D.C. May
3, 1994.
ICI 1992. Vapam® Product Guide. ICI Agricultural Products.
Wilmington, DE.
Larson and Shaw 1994. "Evaluation of Eight Preplant Soil Treatments
for Strawberry Production in Southern California". 1994 International
Conference on Methyl Bromide Alternatives and Emissions Reductions.
Kissimmee, FL.
Lykes Agrisales 1995. Price Quote. Active Ingredient Prices for Vapam®
and Methyl Bromide. Lykes Agrisales, Lake Placid, FL.
Noling and Becker 1994. "The Challenge of Research and Extension to
Define and Implement Alternatives to Methyl Bromide". Supplement to
the Journal of Nematology, Vol 26, No. 4s, pp. 573-586.
Olson and Noling 1994. "Fumigation Trials for Tomatoes and
Strawberries in Northwest Florida". 1994 International Conference on
Methyl Bromide Alternatives and Emissions Reductions. Kissimmee, FL.
November 1994.
Tjosvald 1995. Personal Communication. Steve Tjosvald, Monterey County
Cooperative Extension Service, Watsonville, CA. ICF Incorporated,
Washington, D.C. April 1995.
Yarkin 1994. Methyl Bromide Regulation: All crops should not be treated
equally. Cherisa Yarkin, David Sunding, David Silberman, and Jerry
Siebert, University of California, Davis. California Agriculture, Volume
48, Number 3. May-June 1994.
For more information on this material from the Metam-Sodium Task Force
Product Stewardship Committee (a group of U.S. manufacturers of
metam-sodium), click here. Note
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